Altruism, in biology, is when a living thing engages in behaviors that contribute to the survival and reproduction of others at the expense of its own survival and reproduction. Altruistic behavior is challenging to understand in terms of natural selection. Natural selection is the evolutionary process by which individuals better suited to their environment tend to leave more descendants (see Natural selection). Natural selection would seem to favor individuals who act selfishly over individuals who act altruistically. For example, a selfish individual might survive a famine by hoarding food. An altruistic individual who shares food, on the other hand, would more likely starve to death.
In time, the greater reproductive success of selfish individuals should lead to the spread of selfish traits, eliminating altruism from nature. Despite this tendency, altruistic behavior remains common in nature. For example, a worker honey bee collects nectar that sustains the queen bee and her offspring. The worker’s behavior is clearly altruistic, because it benefits the queen and her offspring at the worker’s expense. Human beings also engage in altruistic behaviors, and helping others is important to human morality. Helping others may cost an individual money, time, or other resources that could otherwise benefit the individual’s offspring.
Scientists have developed theories to describe how altruism could evolve through natural selection. One such theory, first proposed by the British naturalist Charles Darwin, has become known as group selection. According to group selection, groups of altruistic individuals may outcompete groups of selfish individuals, leading to the spread of altruistic traits. For group selection to work, some groups must have more altruists than others. One way that this arises is when groups are composed of close relatives who share the same genes (basic units of inheritance). This kind of selection for altruism is called kin selection. Many scientists now regard kin selection as a form of group selection.
See also Group selection; Kin selection.
